Hydraulic flywheel



United States PatentO HYDRAULIC FLYWHEEL Clarence J. Coherly, San Marino, Califi, assignor to Kobe, Inc., Huntington Park, Califi, a corporation of California Application February 4, 1955, Serial No. 486,124

11 Claims. (Cl. 60-51) The present invention relates in general to regulation of the rate of flow of operating fluid from a source of such fluid to a device utilizing same, and a primary object of the invention is to provide a method of and apparatus for maintaining the rate of flow of operating fluid from the source to the device substantially constant despite a tendency on the part of such device to receive operating fluid at a variable rate.

As a matter of convenience, the invention will be considered herein in connection with a fluid operated oil well pump of the reciprocating type, although it will be understood that the invention is not necessarily limited thereto and is susceptible of other applications.

As a general background, a fluid operated pump of the type indicated includes interconnected motor and pump pistons which are reciprocated in unison in their respective cylinders by periodically reversing an operating-fluid pressure differential applied to the motor piston. For this purpose, the pump is provided with a control valve which regulates the application of operating fluid pressure to the motor piston, the operating fluid usually being relatively clean crude oil. The pump piston, as it is reciprocated by the motor piston in this manner, pumps fluidifrom the well to the surface as production fluid.

An undesirable operating characteristic of such a pump is that it tends to operate unevenly, i. e., at a variable speed, when operating at low speeds with high operating fluid and production fluid pressures. One reason for this undesirable operating characteristic is that the lubricating properties of the operating fluid are not constant since the operating fluid is usually, as hereinbefore indicated, crude oil which is only relatively free of abrasive material and water. As will be apparent, the lubricating properties of such an operating fluid will vary widely, depending upon the crude oil utilized. Coupled with the inherently low lubricating value of such an operating fluid, the bottom hole temperature, i. e., the temperature in the well at which the pump operates, may be quite high, e. g., 300 F., which further reduces the lubricating value of the operating fluid. Also, variations in the condition of the various parts of the pump will produce uneven operation.

Another important factor responsible for uneven pump.

operation is the effect of starting friction, which is much higher than running friction, it being noted that the pump stops, at least momentarily, at each end of the motor piston stroke. The effect of starting friction is important in other equipment also, but is particularly important in the case of a pump of this character where starting friction may be quite high due to the low lubricating valueof the operating fluid utilized, and due tothe aggravation of the situation by the frequent presence of abrasive particles in the operating fluid. Such abrasive particles are frequently forced into clearances between the stationary and movable parts of the pump, and when the movable parts are stationary with high pressure differentials present, leakage occurs and abrasive particles 2,743,581 Patented May 1, 1956.

accumulate in the clearances. The longer the movable parts of the pump remain stationary, the more solid matter accumulates in the clearances between the movable and stationary parts. Thus, the starting friction increases with standing time and one object of the invention is to eliminate or materially minimize standing time.

With prior fluid operated pump systems, when the pump stops, a substantial period of time is required to increase the operating fluid pressure at the pump to a value sufficiently high to start the pump again. The time required to produce the necessary pressure increase depends upon the volume of operating fluid. in the tubing system between the bottom hole pump and the surface pump which pressurizes the operating fluid, the operating fluid pressure, the compressibility of the operating fluid, the expansibility of the tubing system, and the rate at which the operating fluid is supplied to the tubing system by the surface pump. (The effect of tubing system expansion on the time to produce a pressure increase sufficient to start the bottom hole pump is small as compared to the effect of the compressibility of the operating fluid and is neglected in the illustrative example which follows, it being understood that the effect of tubing system expansion is to further increase the pressure build-up time.) Since the volume of operating fluid in the operating fluid tubing increases directly with the length of the tubing, and the operating fluid pressure increases directly with the pumping head, the volume of operating fluid which must be pumped into the tubing system to produce a predetermined pressure increase at the bottom hole pump varieswiththe well depth. Thus, the time required to obtain a predetermined pressure increases at the bottom hole pump varies directly with the Well depth and inversely with the rate at which operating fluid is supplied to the operating fluid tubing by the surface pump. Under many operating conditions, the time required to increase the pressure of the operating fluid at the bottom hole pump as little as 50 p. s. i. to overcome starting friction may become quite appreciable.

Considering by way of example a two-inch pump of the so called free type operating at ten strokes per minute (S. l. M.), the rate of flow of operating fluid for steady operation would be 0.63 gallon per minute (G. P. M). With such a pump, and assuming that the free pump is in the operating fluid tubing, the volume of operating fluid in the resulting two-inch tubing is 162 gallons per thousand feet of tubing. Assuming that the pump is set at 6,000 feet and that the operating pressure is 2,500 p. s. i. gauge, the operating fluid, assuming a typical crude oil, will be compressed by 0.24 gallon to produce a pressure increase of 50 p. s. i. Therefore, the time required to obtain a pressure increase of 50 p. s. i. at the bottom hole pump is equal to 0.24 divided by 0.63, or twenty-three seconds, under the conditions specified. If the pump were operated at 1 S. P. M., instead of 10 S. P. M., as is frequently desirable, the time required to increase the operating fluid pressure to 50 p. s. i. would be ten times the foregoing value, or 3.8 minutes. If the starting friction is such that an increase in operating fluid pressure at the pump of 300 p. s. i. is required to start the pump, such a pressure increase being not unusual if the pump has been standing for an appreciable time, nearly twenty-three minutes would be required to build up the operating fluid pressure to this extent with operating fluid supplied by the surface pump at a rate corresponding to 1 S. P. M. for the bottom hole pump, all other conditions being equal.

Considering in more detail the case in which twentythree minutes are required to build up the pressure sufficiently to overcome starting friction, which corresponds to a pressure build-up of 300 p. s. i. and a desired pump speed-of l S. P. M., the pump, when it finally starts,

will run at a very high speed until theexcess pressurehasbeen dissipated. In fact, the first few strokes may be at speeds very much higher than the rated speed of the pump, which isobviously undesirable. in practice, the excess pressure may be dissipated within about one minute, whereupon the pump stops again and" remains stopped untilthe pressure again builds up sufliciently to re-start it. Thus, where twenty-three minutes are required to build up the operating fluid pressure sufficiently to-overcomestarting friction, the pump may stand for twenty-three minutes and then run for one minute, or less. Thus, while, in the long run, the pumpinay make twenty-fourstrokes in twenty-four minutes, for an average speed of: l S. P. ML, all. twenty-four strokes may take place in less than onerninute, which is undesirable forv many'reasons, paramount among which is the possibility of: damage to the pump if it makes the first few strokes-at speeds: in excess of itsrated speed.

Theforegoing examples, which are intended as illustrative only, ignore the effects of fluid friction and inertia of the; moving parts of the bottom hole pump. Both fluid friction and inertia tend to smooth out the operation and prevent such intermittent action, but the effect of these factors is negligible at low speeds and tends to produce steady operation only at pump speeds in excess of to S. P. M. when operating at high pressures. Considering an example of the effect of fluid friction, an increment of operating fluid pressure of approximately 30 p. s. i. may be required to maintain operating fluid flow throughout the entire-system when the rate of operating fluid flow is such as to tend to operate the bottom hole pump at 20 S. P. M. Consequently, when the pump stops, this increment of operating fluid pressure is available to help restart the pump. However, the corresponding increment of operating fluid pressure for a rate of operating fluid flow tending to produce a pump speediof. 1 S. P. M. is insignificant so that fluidfriction is not much of a factor at'very low speeds.

Considering the. influence of inertia eflects in tending to smooth out operation, inertia effects provide forces which at least partially offset increases in friction as the pump slows down. Under a set of conditions unnecessary to outline, here, the kinetic energy of the moving parts of the pump may be suflicien-t at a pump speed of 30 S. P. M. to carry the motor and pump pistons a distance of 0.0i inch against frictional resistance. corresponding to an operating fluid pressure increment of 300 p. s. i. However, at a pump speed of 1 S. P. M. under the. same conditions, the kinetic energy of the moving par-ts of the pump would carry the motor and pump pistons a distance of only 0.0000125 inch. Thus, it will be seen that, at low pump speeds, the eflect of inertiain smoothing out operation is negligible.

In the light of the foregoing, an important object of the invention is to provide means for maintaining the speed of the pump substantially constant despite extreme variations in the resistance encountered by the pump.

,More particularly, an object of the invention is. to

provide a high kinetic energy system in series with one of low kinetic energy so that the combined system will operate against a variable load at a substantially constant speed. Another object is to provide a high kinetic energy systern in series with and closely coupled to one of low kinetic energy so that the compressibility of the operating fluid between the two will not absorb the energy, with the result that the energy of the first system may be transferred to. the second tomaintain substantially uniform speed against a variableload.

Another object is to-provide a rotatingsystem of high kinetic energy in series with and closely coupled to a reciprocating systernof low inertiato maintain-a substantially uniform'speedagain-st a variableloadtin the recip;

Expressed somewhat differently, an object of the invention is to provide a rotary energy storing means, actuable by the flow of operating fluid from a source of such fluid under pressure to a device utilizing the operating fluid for storing kinetic energy for subsequent transfer to the operating fluid supplied to the operating-fluid utilizing device when the load on such device increases. More particularly, an object is to provide, in effect, a fluid operated flywheel actua ble by the flow of operating fluid to the device for storing kinetic energy and for transferring such energy to the operating. fluid supplied to the device in response to a load increase.

Another object is to provide an energy storing means or flywheel which includes a rotor and means for rotating the rotor in response to; operating fluid flow from the source to the device utilizing such fluid, the kinetic energy stored in the rotating rotor being transferred to the operating fluid supplied to the device in response to an increase in the load thereon. More particularly,- an object of the invention is to provide such an energy storing means having an inlet connected to the" source of operating fluid and an outlet connected to the device requiring the operating fluid, the rotor carrying means for rotating it as the operating fluid flows fromthe inlet to the outlet:

Another object is to provide the rotor with cylinders having therein pistons which are displaced in one direction by the operating fluid entering the energy storing means through the inlet and which are displaced in the opposite direction to discharge the operating fluid into the outlet, the energy storing means being providedwith valve means for alternately connecting each cylinder with the inlet and the outlet.

Another object is to provide cam means engagingthe pistons for displacing the pistons in said opposite direction to discharge the operating fluid into the outlet.

Another object is to provide an energy storing means of the foregoing nature wherein the cylinders are sub stantially parallel to the axis of rotation of the'rotor and wherein the cam means for displacing the pistons 'insaid opposite direction is inclined at an angle to the axis of rotation of the rotor.

Another object is to provide a cam means'of the foregoing nature which comprises the outer race of a ball bearing set at an angle to the axis of rotation of the rotor, the outer race of such bearing engaging one end of' each piston.

While such an energy storing means interposed between a source of operating fluid under pressure and a device utilizing such fluid has advantages in'systems of various types, it has particular advantages in a system wherein the device utilizing the operating fluid is a" reciprocating system, suchas a bottom hole oil wellpump as hereinbefore discussed. In such a system, the invention provides a means of obtaininguniform strokes in afiuid operated bottom hole pump, provides a means of exerting aforce on the motor piston which will carry the motor and pump pistons over peak loads, provides a means for preventing stoppage of the pump with normal variations in friction, and provides a means of preventing excessive pump wear due to constant stopping and starting of the pump and due to excessive operating speeds encountered after prolonged stoppage with prior systems.

Another important advantage of the present invention is that it avoids the-throttling losses encountered in prior systems wherein the source pressure ismaintained high enough to overcome anticipated starting friction and wherein a throttling device is utilized in close proximity to the pump to control the rate of flow of operating fluid to the pump. In such a prior system, the source pressure is always equal to at-least'the maximum pressure required to operate the pump, whereas, with the present invention, thesource pressureneeds beonly the average pressure. requiredto operate. the pump, the energy storing means. of theinvention adding or subtracting from; the

pressure of the operating fluid supplied to the pump as required to meet varying loads on the pump. Thus, the energy losses of systems employing throttling devices are eliminated, which is an important feature.

The foregoing objects, advantages and features of the present invention, together with various other objects, advantages and features thereof which will become apparent, may be attained with the exemplary embodiment of the invention illustrated in the accompanying drawing and described in detail hereinafter. Referring to the drawing:

Fig. 1 is a vertical sectionalviewrof an oil well pumping system in which the fluid operated energy storing means or flywheel of the present invention is incorporated; r

Fig. 2 is an enlarged, vertical sectional view taken along the arrowed line 2-2 of Fig. 1 and showing the fluid operated flywheel of the invention;

Figs. 3 and 4 are transverse sectional views respectively taken along the arrowed lines 33 and 44 of Fig. 2;

Fig. 5 is a vertical sectionalview taken along the arrowed line 55 of Fig. 4; and r r Fig. 6 is a transverse sectional viewxtaken along the arrowed line 6--6 of Fig. 2.

Referring first to Fig. l of the drawing, the numeral10 designates an oil well casing provided with perforations 12 to admit into the casing fluids from surrounding formations 14. At the upper end of the casing 10 is a casing head 16 which supports an operating fluid or power tubing 18 and a production tubing 20. At the bottom of the power tubing 18 is an inlet fitting 22 which admits well fluid into and serves as a seat for a fluid-operated bottom hole pump 24 of the so-called free type. The pump 24 is provided with the usual motor and pump pistons 26 and 28, the motor piston being reciprocated in its cylinder by periodically reversingthe direction of application of an operating-fluid pressure differential thereto under the control of a suitable control valve means, not shown, incorporated in the pump, as is well known in the art. The pump piston 28 takes fluid from the well through the inlet fitting 22 and discharges it through a passage 30 into the production tubing 20, which conveys the well fluid to the surface as production fluid, all as is well known in the art also. L

The power and production tubings 18 and 20 are connected at their upper ends to a pump head 32 containing valve means,'not shown, operated by a handle 34 for regulating fluid flow through the tubings 18 and 20. With the handle 34 in one position, an operating fluid under pressure from a suitable source, e. g., a surface pump such as a triplex pump, is delivered to the power tubing 18 to operate the pump 24 in a manner to be described, and production fluid discharged by the pump flows from the production tubing 20 into a line leading to a suitable point of storage, or the like. With the handle 34 in another position, the flow through the system is reversed, the operating fluid under pressure being delivered to the production tubing 20 so that it acts on the lower end of the pump 24 to move the pump upwardly through the power tubing 13 to the surface, all as is well known in the art.

With the foregoing background, the invention will now be considered in more detail. As best shown in Figs. 1 and 2 of the drawing, connected to the upper end of the pump 24 and movable through the power tubing 18 therewith is a fluid operated energy storing means or flywheel 40 of the invention through which the operating fluid must flow from the power tubing 18 into the pump 24. The

flywheel 40 is interposed between the usual packer mandrel 41 connected to the upper end of the pump 24 and the usual free pump nose 42, the latter having inlet ports 44 therein through which the operating fluid may flow from r the power tubing 18 into the interior of the nose 42.

Referring particularly to Fig. 2 of the drawing, the

energy storing means 40 includes a housing or barrel 46 into the upper end of which is threaded a fitting 48, the lower end of the nose 42 being threaded into this fitting. Threaded into the lower end of the barrel 46 is a coupling 50 which, in turn, is threaded into the upper end of the packer mandrel 41. The nose 42 serves as an inlet for the flywheel 40 and the coupling 50 serves as an outlet therefor.

The fitting 48 is provided therein with passages 52 which communicate at their upper ends with the flywheel inlet and which communicate at their lower ends with an arcuate inlet port 54 in the lower end of the fitting, this port being less than 180 in angular extent. Also formed in the fitting 48 diametrically opposite the inlet port 54 is an arcuate outlet port 56, also of less than 180"v in angular extent. The outlet port 56 communicates with passages 58 in the fitting 48, the passages 58 communicating, in turn, with an annular space 60 between the barrel 46 and a cylindrical rotor 62 coaxial with the barrel. The annular space 60 communicates at its lower end with passages 64 in a fitting 66 in the barrel 46 adjacent the lower end thereof, the passages 64 communicating at their lower ends with the flywheel outlet leading to the pump 24. Interposed between the upper end of the rotor 62 and the lower end of the fitting 48 is a valve member or disc 70 which is connected to the rotor 62 to rotate therewith, as by pins 72, Fig. 5, the rotor being carried by a shaft 74 on bearings 76. The ends of the shaft 74 extend into bores in the fittings 48 and 66 and are keyed, or otherwise secured, therein.

The rotor 62 is provided with a plurality of cylinders substantially parallel to the axis of rotation of the rotor and containing pistons 82. The upper ends of the cylinders 80 communicate with arcuate ports 84, respectively, in the valve disc 70, the ports 84 communicating alternately with the arcuate inlet port 54 and arcuate outlet port 56 in the fitting 48 as the rotor and valve disc rotate. Thus, the upper end of each cylinder 86) is alternately placed in communication with the flywheel inlet and the flywheel outlet as the rotor 62 rotates.

It will be apparent that, when the valve means formed by the valve disc 70 and the cooperating ports 545nd 56 connects each cylinder 80 to the flywheel inlet, the operating fluid under pressure will move the corresponding piston 82 downwardly. When the valve means connects each cylinder 80 with the flywheel outlet, the corresponding piston 82 is moved in the opposite direction, i. e., upwardly, by a cam means engaging the lower ends of the pistons 82 and inclined at an angle to the axis of rotation .of the rotor 62, the cam means serving to rotate the rotor in response to downward piston movement in a manner which will be apparent. This cam means comprises a ball bearing 92 having an inner race 94 encircling an inclined cylindrical projection 96 on the fitting 66, and having an outer race 98 on which the lower ends of the pistons 82 are seated.

As will be apparent, when the valve means connects the upper end of each cylinder 80 with the flywheel inlet, the corresponding piston 82 moves downwardly and coopcrates with the cam means to rotate the rotor, the corresponding point on the outer bearing race 98 moving downwardly under such conditions. During the portion of each revolution of the rotor that the upper end of a particular cylinder 80 is in communication with the flywheel outlet, the corresponding point on the outer bearing race 98 is moving upwardly to displace the corresponding piston upwardly. During each downward piston stroke, operating fluid from the source of supply, i. e., the power tubing 18, is admitted into the corresponding cylinder, and during the upward stroke of such piston, operating fluid is discharged from the corresponding cylinder into the fly wheel outlet leading to the pump 24. Thus, the operating fluid passes through the flywheel 40 on its way to the pump 24 and rotates the rotor 62 in the process.

Considering the. over-all operation of the invention, it willbe apparent that as long asthe pump 24' is operating substantially uniformly with only momentary stops at the ends of each stroke, the fluid operated flywheel 40 ofthe.

invention will operate at a substantially constant speed to maintain the level ofstored energy substantiallyconstant, the, rotation of the rotary parts of the flywheel 40 being produced by the action of the operating fluid flowing therethrough on the pistons 82.

Now, assume that the speedof the pump 24' suddenly decreases for some reason, or that the pump fails to start immediately after stopping at one end of a stroke. Consequently, the rate at which the operating fluid is received bygthe pump 24'is reduced, ordecreases. to zero. Under such conditions, the inertia of the rotary parts of the flywheel 40 keeps them rotating so that the pistons 82 act.as, pumping pistons and take operating fluid from the flywheel inlet and discharge it at a higher pressure into the. flywheel outlet. Thus, the operating. fluid pressure supplied to the pump 24 is increased, it being noted that compressibility eifects are negligible because of the fact that the pump 24 and theflywheel 40 are closely coupled. Thus, the energy stored in the rotatingparts of the flywheel 40' is transformed into an increase in the pressure suppliedto the pump 24 torestore the speed of the pump to normal almost instantaneously. As soon as the load increase on the pump 24 has been overcome in .this manner, normal operating fluid flow through the flywheel 40 is restored with. a resultant increase in the speed of the rotary parts of the flywheel to the normal value and a resultant increase in the stored energy level to normal.

Thus,v the energy storing means or flywheel. 4.0 of the present invention is actuated by the operating fluid' flowing therethrough from the operating fluid source to the device utilizing the operating fluid to store energy which is transferred to the device utilizing the operating fluid when the operating flow rate thereto decreases for any reason, such as an increase in resistance to movement of the moving parts of the pump 24.. Thus, considering the pump 24 specifically, it operates at a substantially constant speed, any tendency for the speed thereof to decrease resulting in an immediate increase in the operating fluid pressure supplied thereto dueto energy transformation from kinetic to potential. This stabilizing infi'uence on the operation of the pump 24 has numerous advantages, as hercinbefore discussed. Itwillbe understood'that the total mass of the rotating parts of the fluid operated flywheel of the invention, and the speed of rotation thereof, are so selected as'to provide the desired kinetic-energy storage capacity, the number of pistons 82 and their size and stroke determining the rotational speed, which may be 5,000 R. P. M., for example. A flywheel of suitable size, such as could be used with the two-inch pumpgiven as an example in this description of the invention, may weigh approximate-lyfive pounds and, it operated at 5,000 R. P. M., would have a stored energy of 40 ft. lbs. This is five hundred times the kinetic energy of the moving system ofthe pumpwhen running at 20 strokes per minute, and one hundred and twenty-five times the kinetic energy when running at a speed of 80 strokes per minute. Since the problem of smooth operation is largely-limited to pumps running 20 strokes per minute, or less, a five-hundredfold increase in kinetic energy is ample to sustain uniform operation. Assuming, for instance, that the starting friction is equivalent to 1,000 p. s. i., the stored energy in the flywheel would. carry the piston a distance of over /2 against this pressure. This is an extreme condition andprobably. seldom, if ever, experienced, except when the. pump or engine has been badly scored, or otherwise damaged.

From the above it can be seen that the amount of stored energyin a five pound flywheelis adequate to produce: large forcesin case the pump speed is suddenly reduced or stopped. It is possible to make a flywheel of considerably.- greater. weight than five pounds, and this figure was taken simply because it is approximately of the invention herein for purposes of illustration, it

will be understood that various changes, modifications and substitutions maybe incorporated in such embodiment without departing from the spirit of the invention as defined by the patent claims appearing hereinafter.

I I claim-is myinvention:

"1". In combination: a source of operating fluid at a normal pressure; an operating-fluid consuming device connectedto said source and occasionally requiring operating fluid at a pressure in excess of said normal; and energy storing means interposed between said source and said device and actuable 'by' operating fluid flow from said source to'said device for storing energy when the operat ing fluid pressure requiredby said device is not in excess of said normal and for increasing the pressure of the operating'fl'uid" supplied to said device by transferring stored energy thereto when the operating fluid pressure required by saiddevice is in excess of said normal.

'2; Incombination: a source of operating fluid under pressure; an operating-fluid consuming device connected to saidsource and normally' consuming operating fluid therefrom-atapredeterminedrate; and means interposed betweensaid sourceandsaid device and actuable by. operatingfluidflow'f'rom-said source to said device and respon= si-ve to: adecrease in the rate of operating fluid flow-t0 said device below said predetermined rate for increasing thepressure of the operating fluid delivered to said' device.

3a. Incombination: a source ofoperating fluid under pressure; an A operating-fluid consuming device connected to said source and normally consuming operating fluid therefrom at a predetermined rate; and rotary energy storing means interposed betweenv said. source and said device; andi-actuabletby operating fluid flow from. said sourceto saidf devicerand'responsive to a decrease in.the rate oftoperating. fluid' flow to said device below said predetermined rate for increasing the pressure of the operating fluid deliveredto said device.

4. In. combinatibnpasource of operating fluid under pressure; :an operating-fluid consuming device; andkinetic energy storingtmeans interposed between and connected inseries'w-ithsaid source and said device and havingan inlet connected'to said source and an outlet connected to saidxdevicqisaid: means including a rotor provided with cylinders: having pistons therein and including valve means responsive to rotation of said rotor for alternately con nccting one. end' of 'each cylinder to said inlet and said outlet, operatingfluid admitted to said one end of each cylinder by said valve means producing movement of the pistoninsuclrcylinder in one direction, said means includingmeans for moving eachpiston in the opposite directionwhen said one end of the corresponding cylinder is connected to said outlet by said-valve means, and including means for rotating said rotor.

5. Inan. apparatus for maintaining substantiallyv constant delivery of' operating fluid from a source of such fluid under pressure to an operating-fluid utilizing device despite a tendency ofsaid device to utilize operating fluid at varying rates, said apparatus being interposed between and connected" in series with said source and said device, and including: ahousing having an inlet connected to said source and an outlet connected to said device; a rotor in saidhousing and provided with cylinders having pistons therein; valve means responsive to rotation of said; rotor for connecting one end of each of said cylinders alternatelyto said inlet and said outlet, operating fluid admitted" to said one end of each cylinder by said valve means displacing the piston in such cylinder in one direction; means for displacing each piston in the opposite direction when said one end of the corresponding cylinder is connected to said outlet by said valve means; and means responsive to movement of said pistons for rotating said rotor.

6. An apparatus for maintaining substantially constant delivery of operating fluid from a source of such fluid under pressure to an operating-fluid utilizing device despite a tendency of said device to utilize operating fluid at varying rates, said apparatus being interposed between and connected in series with said source and said device, and including: a housing having an inlet connected to said source and an outlet connected to said device; a rotor in said housing and provided with cylinders having pistons therein; valve means responsive to rotation of said rotor for connecting one end of each of said cylinders alternately to said inlet and said outlet, operating fluid admitted to said one end of each cylinder by said valve means acting on one end of the piston in such cylinder to displace such piston in one direction; and cam means engaging the other end of each piston for displacing such piston in the opposite direction when said one end of the corresponding cylinder is connected to said outlet by said valve means and for rotating said rotor.

7. An apparatus as defined in claim 6 wherein said cylinders are substantially parallel to the axis of rotation of said rotor.

8. An apparatus as defined in claim 7 wherein said cam means includes a ball bearing inclined at an angle to the axis of rotation of said rotor and having an outer race which engages said other ends of said pistons.

9. An apparatus as defined in claim 6 wherein said valve means includes a member engaging said rotor adjacent said one ends of said cylinders, said member having inlet and outlet ports therein of less than 180 in 10 angular extent with which said one ends of said cylinders are adapted to alternately communicate and which communicate with said inlet and said outlet, respectively.

10. In an apparatus for regulating the flow of operating fluid from a source thereof to a device utilizing such operating fluid, the combination of: a housing having an inlet and an outlet for connection to said source and said device, respectively; a rotor in said housing provided with cylinders having pistons therein, said cylinders being substantially parallel to the axis of rotation of said rotor; valve means for alternately connecting one end of each of said cylinders to said inlet and said outlet, whereby to produce displacement of each of said pistons in one direction in its cylinder when said valve means connects said one end of such cylinder to said inlet; and cam means inclined with respect to the axis of rotation of said rotor and engaging said pistons for producing movement of each piston in the opposite direction in its cylinder when said one end of such cylinder is connected to said outlet by said valve means and for rotating said rotor.

11. A method of maintaining substantially constant the rate of flow of operating fluid from a source of such fluid to a device utilizing same despite any tendency for said device to receive operating fluid at a variable rate, including the steps of: removing energy from the operating fluid flowing to said device and storing such energy as kinetic energy when said device tends to receive operating fluid at a high rate; and transferring energy from said stored kinetic energy to the operating fluid flowing to said device when said device tends to receive operating fluid at a low rate.

References Cited in the file of this patent UNITED STATES PATENTS 2,625,109 Coberly Jan. 13, 1953 

